Creating Value from Desalination Waste: Magnesium Recovery from Desalination Brine by Cation Exchange

Abstract

The motivation for this study was to research whether minerals can feasibly be recovered from desalination waste brine in order to help finance the very expensive process of desalination. Desalination brine is mineral rich but is typically disposed of without reuse. The objective was to assess the most profitable mineral and associated extraction technology to determine whether collocation of a mineral recovery plant with a desalination plant in San Diego could add value to the desalination process. The ultimate purpose of this assessment would be to create a model that developing nations could use to finance desalination. In evaluating the feasibility of this, the technologies associated with mineral recovery were analyzed and compared. To determine the feasibility and profitability of collocation, the first step was to assess which of the following minerals would be most profitable to extract and sell: sodium, magnesium, calcium, or potassium. After establishing that magnesium would likely be the most valuable ion to recover from desalination brine, the different technologies associated with mineral extraction were assessed. It was determined that cation exchange with the Lewatit TP 260 resin was the most feasible technology. Finally, a profit analysis was performed to determine how much magnesium could be extracted and sold and whether using the Lewatit TP 260 resin would make sense economically. It was found that the process has the potential to be economical, taking into account the cost of the resin, the regenerant, and the capital cost of building a magnesium extraction plant. The system could potentially generate as much as $640 million in profit per year, not including capital costs of building the plant and the cost of the resin, which could be over $1 billion. This study is the first to analyze the minerals in desalination brine for the purpose of creating a profit. It includes relevant methodology, analyses, and comparisons of mineral extraction technologies for researchers interested in creating value from desalination brine.